Prop Bet

A prop bet (short for proposition bet) is any bet that isn’t on the game’s final outcome. Player props (how many yards Mahomes throws), game props (will there be overtime), and exotic props (which team scores first) are all prop bets. They’ve exploded in volume since the 2018 PASPA repeal — props now make up a big chunk of US sportsbook revenue.

Player props

The most common prop type. Bet on whether a player goes over or under a stat line:

• Mahomes Over 287.5 passing yards
• LeBron Under 26.5 points
• Tatum Over 7.5 rebounds

Both sides are typically priced -110 / -120 with built-in vig. Lines reset constantly during the season as players’ form shifts.

Game props

Bet on something about the game that isn’t the final score:

• First team to score
• First-quarter point total
• Will there be overtime?
• Total field goals attempted
• Largest lead at any point

Why prop vig is so high

Most prop markets are less liquid than spread/moneyline/total markets. Less action means books can’t sharpen the line via market efficiency — so they post wider lines (more vig) to protect themselves.

Typical vig:

• Standard spread/total: ~4.5–5%
• Star-player props (Mahomes, LeBron): ~5–8%
• Mid-tier player props: ~8–12%
• Niche / first-time-poster props: 15%+

Props in parlays

Multiple props can be parlayed straight (independent legs) or combined as a same-game parlay. Cross-game prop parlays multiply implied probabilities cleanly. Same-game prop parlays (mixing props from one game) are priced by the book’s correlation model — see SGP for the math.

Where edges hide in props

The prop market is where most retail-sharp edges still exist. Reasons:

• Books can’t sharpen niche markets without volume
• Player projections are model-driven; some books use weaker models
• Beat-writer info (injuries, locker-room stuff) propagates faster than line updates

The catch: books quickly limit accounts that hit props consistently. Treat any prop edge as fragile — it’ll close fast or get capped.

Common pitfalls

• Stat-padding mistakes — late garbage-time stats blow up an under, especially in NBA player props.
• Same-game prop correlation — these are correlated; don’t model them as independent.
• Public-leg props — popular star-player overs are usually shaded by public action.